cause i dont know exactly what youre after

On a second read, I think I should have worded the question in the titel and parts of the post differently. It’s probably not all important that the interpreter frontend is the LSP server as much as that they live in the same process. Because what the graphics are supposed to show is, this would avoid manually feeding the LSP server with function signatures.

That was helpful, thanks.

As for LSP specifically, and in particular for Q2 & Q3: You are correct, those were meant to be very specific to session management and capabilities of existing, established protocol implementations of LSP. Would an implementation of those work without modifying editors? Looking at VSCode, LSP seems to be more of a guideline and it expected to provide your own LSP client plugin anyway, so it probably is less of a problem there. But some editors (e.g. Helix and Emacs) apparently have their official implementation.